JP-A-H 11-262213 and JP-B 3235444 (U.S. Pat. No. 5,914,549) disclose structures of side-mount type alternators that are mounted on engines of vehicles.
In JP-A-H 11-262213, as shown in FIG. 7, an alternator 100 has three stays 120 that are integrally formed with a frame 110. The alternator 100 is fastened on an engine bracket 200 with bolts 130 penetrating mounting holes 121 that are provided in the stays 120, as shown in FIG. 8.
Each of the stays 120 is formed so that a penetrating axis of the mounting hole 121 (i.e. the axis of the bolt 130 penetrating the mounting hole 121) is orthogonal to an axis of a rotating shaft, not shown in the figures, of the alternator 100. Therefore, the alternator 100 is mounted on the engine bracket 200 so that the axis to which the alternator 100 is fastened to is orthogonal to the axis of the rotating shaft of the alternator 100. This type of alternator is known as a side-mount type.
Generally, a plurality of intake windows 140 and a plurality of exhaust windows 150 are formed on the frame 110 to provide air cooling of high temperature components such as a rotor, a stator, an IC regulator and a rectifier (diodes).
In the side-mount type structure, as disclosed in JP-A-H 11-262213 and as shown in FIG. 8, with respect to the penetrating direction of the mounting holes 121 (horizontal direction of FIG. 8), the outermost surface of the frame 110 protrudes to the engine side beyond a mounting face 122. Therefore, a space 300 between the frame 110 and the engine bracket 200 is very narrow. As a result, the ventilation is poor.
Under the above circumstances, at the engine side of the alternator 100, hot air after cooling the inside of the frame 100 and being exhausted from the exhaust windows 150 does not flow smoothly and tends to stay at the space 300. The hot air at the space 300 is reintroduced from the intake windows 140 into the inside of the frame 110. As a result, it is insufficient to cool the inside of the frame 110 and the lifetime of the high temperature components of the alternator 100 that need to be cooled is severely shortened. Furthermore, the power output of the alternator 100 falls because of insufficient cooling of the rotor and the stator accommodated in the frame 110.